国際会議
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Efficient Threshold Public Key Encryption from the Computational Bilinear Diffie-Hellman Assumption
- 著者
- M. Ebina, J. Mita, J. Shikata, and Y. Watanabe
- 会議名
- APKC 2021
- ページ
- 23–32
- 出版社
- ACM Press
- 発行年
- 2021
- 発表日
- 2021/6/7
Abstract
In this paper, we show the first efficient threshold public-key encryption (TPKE) scheme under the difficulty of search problems. More specifically, our TPKE scheme simultaneously achieves: (1) Chosen ciphertext security (CCA security) under the computational bilinear Diffie-Hellman (CBDH) assumption in the standard model; (2) re-splittability, which is a useful property that makes partial secret keys refreshable; and (3) O(kappa)-bit ciphertexts and public keys. Most previous CCA-secure TPKE schemes rely on decisional complexity assumptions or random oracles. Although there exist CCA-secure TPKE schemes under the difficulty of search problems, all such schemes are inefficient or work over small plaintext spaces. Technically, we begin with a direct construction of a threshold identity-based key encapsulation mechanism (TIB-KEM) with a weak security notion. Then, we transform the weakly-secure TIB-KEM into a CCA-secure TPKE scheme via the tag-KEM/DEM approach.